Fampridine (also called 4-aminopyridine or dalfampridine in the USA) is an oral drug recently approved for patients with MS as it can help improve symptoms of walking impairment.
Walking problems, which affect a large proportion of people with MS, may have many causes.
Although not everyone taking fampridine will see improvements in walking, in clinical trials between a third and a half of those taking it found walking speed improved, with an average improvement of about 25 per cent.
Fampridine seems to be more effective in patients who walk very slowly. There are no major contraindications to fampridine, but people with a history of epilepsy cannot take the drug.
In this study, a team at the MS Treatment and Research Center of Minneapolis treated 71 MS patients with fampridine for walking impairment.
Five of these patients had a history of preexisting trigeminal neuralgia (episodes of sudden, severe facial pain originating from the trigeminal nerve).
The researchers observed that, in four of these patients, trigeminal neuralgia worsened when they took fampridine. In three patients, recurrences of facial pain started within a month of starting treatment with fampridine, while in another patient the appearance of severe facial pain occurred after 18 months.
Although fampridine was stopped as soon as patients’ pain started to get worse, in some case the facial pain became resistant to medication.
These results suggest that fampridine can cause a reactivation of neuropathic pain due to trigeminal neuralgia.
This means that fampridine must be used with caution in people with a history of MS-related trigeminal neuralgia.